1. Field
The subject invention is in the field of pianos and, more specifically, in the field of sound board assemblies used in pianos. Still more specifically, it is in the field of the bridges, ribs and cut-off bars used in sound board assemblies and, in particular, the cut-off bars.
Prior Art
In manufacturing pianos, particularly upright pianos, considerable attention is addressed to the problems involved in providing desired tonal qualities and in avoiding tonal discontinuities along the scale of the piano. For example, the rate of decay of the tones produced in the range of the fifth octave of the piano may tend to be too rapid. Also substantial tonal discontinuity may occur between the higher notes produced by strings supported on the bridge for the bass strings (i.e. the bass bridge) and the lower notes produced by strings supported on the bridge for the tenor strings (i.e. the tenor/treble bridge).
Various techniques have been and are used in prior art pianos to minimize and attempt to avoid inconsistencies and discontinuities in tonal qualities and characteristics along the scale of a piano. FIGS. 1, 2 and 3 attached schematically illustrate examples of prior art techniques used on rectangular sound board assemblies and all involve the use of cut-off bars. Cut-off bars are pieces of structure attached to the sound board of the sound board assembly and to the frame to which the sound board is attached, the technical term for such a frame being the liner. Cut-off bars define and limit the effective working area of a rectangular sound board.
The sound board assembly in FIG. 1 comprises sound board 10, liner components 11, 12, 13 and 14, ribs 15 through 23, cut-off bars 24 and 25 and bridges 26 and 27 attached to the face of the sound board opposite to the face showing in this view. The phantom lines in all the drawings indicate the shapes and positions of bridge attached to the sound boards. Both cut-off bars are attached to the sound board and, at each of their ends, to a liner components. The sound board assemblies in FIGS. 2 and 3 are basically the same as that of FIG. 1, differing only in details of rib and bridge spacings and placements and in cut-off bar sizes and placements and, in the case of cut-off bar 28 in FIG. 3, the curved instead of straight shape. It is stated here for reference purposes that the operation of sound board assemblies is a function of the amounts and distribution of stiffness and mass over the area of the board and that the liner and cut-off bars effectively present infinite mass and stiffness where they contact the sound board.
These configurations, and others, have alleviated to various degrees and not eliminated the problems of discontinuities in tonal qualities and characteristics along the scale of a piano.
Accordingly, the primary objective of the subject invention is to provide a better solution to the problems noted above. Secondary objectives are that the solution be easily implemented and adapted to tuning techniques not possible in prior art solutions.